HP 17bll+ User Manual page 231

If the calculator responds to keystrokes but you suspect that it is
malfunctioning:
1. Do the self-test (described below). If the calculator fails the self test,
it requires service.
2.
If the calculator passes the self-test, it is quite likely you've made a
mistake in operating the calculator. Try rereading portions of the
manual, and check "Answers to Common Questions" on page
222.
3. Contact the Calculator Support department.
A: Assistance, Batteries, Memory, and Service 231